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Blowtorches, tweezers and glue: These are just a few of the items used to create those mouth-watering restaurant ads.

To make food look as appealing as possible, food stylists and photographers use a range of instruments, good lighting, fresh ingredients and attention to detail. These tricks of the trade help explain why restaurant meals from the drive-thru often look very different than they do in promotional images.

Some of the tools that a food stylist would use during a photo shootToday

"Nothing is just plopped down and put in the center like it is when you order at a restaurant," said Jean Ann Bybee, owner of Bybee Photography and co-author of a pair of books about food styling.

"Let's say we're shooting a beef burger. It may not be cooked all the way through because we want to maintain the size of the burger," said Janine Kalesis, a food stylist who has worked with Chipotle Mexican Grill andKraft's Velveeta.

Once cooked, meat and vegetables tend to shrink, and vegetables begin to wilt.

Burger King's Big Fish sandwich.Today

"Mainly the reason why we're not cooking things all the way through is it's sitting on set," Kalesis said. "It can sit on set for up to an hour before we have the final shot."

"Companies are so concerned today with overpromising and portion control, so we really have to work with their guidelines," said Nir Adar, a New York-based stylist whose clients have included Chick-fil-A, Yum Brands'Kentucky Fried Chicken, Burger King and White Castle.

While working with Burger King, Adar said he's even had to sign a legal document saying he didn't alter anything. Chick-fil-A demanded that he use its procedures.

"Most companies today want it to be fresh, natural, not overworked," Adar said.

McDonald's, Burger King, Starbucks, Chipotle and Yum Brands didn't respond to CNBC email requests for comment about the practice of food styling. A Chick-fil-A spokeswoman said the company isn't sure it would "be a fit for this story" since it takes a different approach to using food in its commercials, which often center on cows advising people to 'eat mor chikin.'

A Wendy's spokesman said about food stylists, "We supply the same ingredients to them as our restaurants receive. We also require that they prepare and build the products to operational procedures. The big difference is how much time we take to get an appealing shot."

In a statement, Dunkin' Donuts Spokeswoman Michelle King said, "Dunkin' Donuts always uses real Dunkin' Donuts product in our advertisements. Our shoot director and food stylist team build the products to the exact specifications provided by Dunkin' Donuts' chefs to match what will be sold in our restaurants. We strive to ensure the authenticity of our products in our advertising."

On the regulatory side, Federal Trade Commission spokeswoman Betsy Lordan told CNBC by email that truth in advertising laws do apply to restaurant menu items displayed in ads. The commission examines both what's implied by and stated in an ad to determine whether it's deceptive.

"There are no specific FTC regulations governing food photos used in advertising, and the FTC has not pursued any cases alleging that food ads are deceptive based only on the photos," she wrote.

If, for example, customers see that McDonald's fries look different in person than in an ad, that would not cause the same regulatory concern as a false claim that a product has special properties, like reducing the risk of illness.

"Consumers frequently purchase food, it's relatively inexpensive, and it's fairly easy for a consumer—without any specialized training—to evaluate whether the food they get looks enough like the food in the picture to justify purchasing it again," she said.

To satisfy curious diners, one fast-food giant has even lifted the veil on a photo shoot.

In a 2012 video, McDonald's Canada attempted to answer the question, "Why does your food look different in the advertising than what is in the store?"

Using the same ingredients that chain locations use, the fast-food giant's photography and styling team assembled a burger that looks markedly different with the help of a computer program and compared it to one from a McDonald's location.

"Here you can definitely see that there's a size difference," said Hope Bagozzi, McDonald's Canada's director of marketing. "The box that our sandwiches come in keep the sandwiches warm, which creates a bit of a steam effect, and it does make the bun contract a little bit. And then the main difference is that we actually took all the ingredients that are normally hidden under the bun, and we pulled them to the foreground so that you can see them."

Despite the differences, the food is in fact real, stressed the stylists CNBC interviewed.

"It's really important to tell everyone that it's real food," Kalesis said. "There's a lot of misconceptions that people are using fake food, and it's just not true."

"You think models wake up looking like that every day? They have a lot of people making sure they look as good as they can—same thing with food," she said.